The invention relates to a fuel system for internal combustion engines having a fuel tank, a fuel pump connected thereto by a conduit, a fuel metering assembly associated with said pump for feeding fuel to said engine and a return conduit extending from said fuel metering assembly to said tank to discharge excess fuel thereto. The unused quantity of fuel flowing back to the fuel tank can become overly heated because of temperatures either within the system or also outside of it. This leads to a breakdown of the fuel into gaseous and more viscous liquid components. Gas bubbles that result from this breakdown of the fuel are a constant problem and can lead to a failure of the fuel being supplied by the pump. However, it is also important that the fuel that contains entrained air be pumped away while still warm, so as not to cause difficulties later when it is cold.
In known fuel systems of this type, the excess fuel quantity is returned without treatment to the supply tank, so that when the quantity of fuel in the tank is at a low level, gas bubbles are easily entrained and fed back into the fuel supply pump.
An apparatus is in fact known, in which the returning fuel flows obliquely into a perpendicularly disposed container from which the induction line of the fuel supply branches off. By means of this return flow into the tank it is possible that the fuel can be virtually entirely consumed. However, in this container no deaeration takes place, since on the contrary, given the high rate of flow into the tank and there being little fuel in the tank, air is additionally carried along by the fuel and mixed therewith.